Owing to rising requirements in terms of the environmental friendliness of motor vehicles, increasingly stringent restrictions apply to internal combustion engines when it comes to emission limit values. Particularly vehicles such as, for example, trucks, construction vehicles or agricultural vehicles have been subject to ever-stricter emission standards over the past years. The requirements stipulated in these standards can often no longer be met only with measures involving engine management but rather they additionally call for the after-treatment of exhaust gases. This exhaust-gas after-treatment, often also in combination with other methods, frequently involves the use of selective catalytic reduction (SCR). In this process, a chemical reducing agent is metered into the stream of exhaust gas. The stream of exhaust gas mixed with the reducing agent subsequently passes through suitable SCR catalytic converters, where the exhaust gases are cleaned by chemical reduction. A proven reducing agent is a 32.5% aqueous urea solution according to DIN 70070, which is referred to as ADBLUE® by the industry or as Diesel Exhaust Fluid (DEF) in the United States.
For this purpose, the vehicles in question have to be equipped not only with the required devices and aggregates for exhaust-gas after-treatment, but also with an additional service fluid tank for the reducing agent, aside from the fuel tank. Particularly in the case of industrial and agricultural tractors as well as small and medium-sized construction equipment, the available space is generally quite limited. The fuel tank is often located on one side of the vehicle in a front section (as seen in the driving direction) and it is filled via the service fluid inlet or a filler neck by means of a nozzle. This section of the fuel tank often has an integrated step which, for safety reasons, is provided with anti-slip ribbing, or else it has a mounted step cover that the vehicle driver or maintenance personnel can use, for example, to clean the windshield or to replace the wiper blades. The arrangement of the fuel tank and of the reducing agent tank regularly poses design challenges since especially small and medium-sized vehicles only have limited installation space available and are subject to a number of additional requirements. For instance, the reducing agent tank has to be mounted securely. At the same time, the reducing agent tank should not be installed in an area where high temperatures prevail since this would accelerate the degradation of the urea solution.
Owing to the exhaust-gas after-treatment, as a rule, every time or every other time the fuel tank is filled, the reducing agent tank also has to be filled up. In order for the filling of the tanks not to be overly laborious, it is necessary for the filler necks of both tanks to be on the same side of the vehicle, preferably close to each other.
German patent application DE 10 2008 023 073 A1 describes a tank for service fluids of motor vehicles that consists of two service fluid tanks.
The first service fluid tank serves to hold a fuel such as, for example, diesel, while the second service fluid tank is provided for another service fluid component. The second service fluid tank is arranged at the side of the fuel tank and is combined with it to form a unit. On the side of the fuel tank opposite from the second service fluid tank, there is a step module with steps. Both tanks have a filler neck through which each individual tank can be filled with the service fluid or the service fluid component.
A similar service fluid tank arrangement is disclosed in German patent application DE 10 2009 045 500 A1, which describes a utility vehicle tank. On the outside, a bracket is welded onto an end wall of the fuel tank. An additional tank is joined to the bracket on the end face that faces away from the end wall. The additional tank has its own service fluid inlet or filling opening on the outside. A similar service fluid tank arrangement is also disclosed in European patent application EP 1 736 350 A2. Here, however, the service fluid inlets are relatively far from each other, which makes the filling procedure more difficult.
Moreover, it is a known procedure to adapt the two service fluid tanks to the shape of the available space as closely as possible, which results in asymmetrical and complex tank shapes. For instance, the service fluid tanks can be nested inside each other, whereby sections of the service fluid tank are shaped with the corresponding service fluid inlet in such a way that both tanks can be filled in an area that is easy for the user to access during the filling procedure. The service fluid tank arrangement described in European patent application EP 2 479 393 A1 comprises a fuel tank that is shaped like steps on one side and that forms an installation space for a reducing agent tank. The reducing agent tank is located underneath a cover that covers the filler neck of the reducing agent tank and that has to be opened in order to be filled. The cover has molded-on steps and it serves as a ladder via which the vehicle is accessible.
Restrictive package requirements and tight installation spaces often do not permit a solution involving nesting. Consequently, the reducing agent tank is also often accommodated in another place in the vehicle, for instance, on the other side of the vehicle. In order to prevent that the vehicle has to be filled from two sides, the reducing agent tank is then provided with a long pipe connector, a tube, a pipe or the like, whose end is configured as a filler neck that is situated in the vicinity of the filler neck of the fuel tank. However, such solutions fall short of the expectations of the operators or users and are often felt to be unattractive makeshift solutions.
From actual practice, a cover for a service fluid tank arrangement is known by means of which the service fluid inlets can be physically combined in a single component. The cover has two openings that are placed over filler necks of the fuel tank and of the reducing agent tank, which are configured as service fluid inlets, so that the filler necks project out of the openings of the cover and the remaining area of the filler necks is covered. Irrespective of the shape of the service fluid tank that is present, a visually attractive result can be achieved since the top of the cover can be designed in any desired manner, thereby covering an area of the vehicle that is unattractive because of technical circumstances. At the same time, however, for design-related reasons, the degree of freedom for the arrangement of the service fluid tanks is greatly restricted. Thus, the two service fluid tanks, especially their filler necks, have to be arranged adjacent to each other, and the filler necks have to be positioned very precisely for installation purposes, which is fairly laborious.